Estark (originally Esturk, Esterk in GBC translations) is a recurring monster in the Dragon Quest series and an antagonist in Dragon Quest IV. Introduced in Dragon Quest IV, he is generally viewed as the Lord of the Underworld and is often one of the most powerful beings in the games he appears in.

Estark is a large demon armed with two swords and has a body that looks more like an insect's exoskeleton than flesh. He has three eyes and a somewhat crazed, open-mouthed grin and is generally portrayed as being golden brown in color, though his original appearance had a cerulean blue color scheme.

Though folklore within the games usually state Estark as having caused troubles in the past, he is almost always asleep when encountered and must be awakened in order to fight. In some cases Estark has been asleep for so long that he can only remember his name and nothing else, not even if he is a good or evil being.

Estark is a powerful demon that can be considered worthy of being a final boss in some respects. In fact, Estark appears as a superboss in nearly all of his subsequent appearances.

He is the current Lord of the Underworld. A thousand years before the game begins, he used the Secret of Evolution to become the ultimate life-form, but was sealed into slumber and entombed under Mamon by the Zenith Dragon.

Roughly three-quarters of the way through the game, the miners in Mamon accidentally uncover the tomb and awaken him, driving all demons wild with the return of their lord. However, the Hero of Dragon Quest IV acts quickly and leads his or her party into the catacombs to fight him. Estark is not fully awake yet and is thus much weaker than he would be otherwise - with his only resistances being 30% woosh and an immunity to crack. He has a 70% resistance to sap and snooze, but due to the way the game is programmed Meena's Kasnooze will put him to sleep 70% of the time.

Estark is a superboss that can be encountered in the post-completion dungeon players can find in Nadiria. As a superboss he is extremely powerful, much more than the main antagonist of the game Grandmaster Nimzo. Estark favors all out offensive attacks, pausing only to use Disruptive Wave. Having Multiheal or Omniheal is necessary to withstand the fierce barrage of attacks. He has no resistance to bang, frizz, or sizz, but has a 20% resistance to crack, 67% for woosh, and complete immunity to zap. Tempting as it is to go all out with offensive magic, it's better to cut into him with Blizzard Blades for extra damage. Furthermore, Estark also has a 33% chance to get hit with snooze, fizzle, and any stun technique. Kasnoozes unique programming will raise this probability, but be warned that Estark will awaken very quickly.

Upon first defeating him, Estark will allow the party to use his personal T'n'T board: "Stark Raving Mad." He is revealed to have a son called Starkers, who will join the party if they manage complete the board. If the player can defeat Estark in 15 turns or less, they will receive the Catas Trophy knick-knack

While Estark (at the time Esterk) is a monster in this game, it is unlikely that it is the same Estark as depicted in other titles, especially since it is a normal monster (though its appearance bears a homage to both him and Psaro). Regardless, the Estarks that are fought are still very powerful and are also one of the monsters that players can assume the class of by mastering other monster classes or by obtaining an Estark's heart. They can be found in the Zion Cave.

"Not only can he pound opponents with Kafrizzle and Kaboom, but he packs a powerful punch as well. Good luck! This emperor of the underworld evolved into his horrific form after hibernating for many millennia." - Dragon Quest IX bestiary

Estark appears as a Legacy Boss, obtained after completing Quest #152 (or received at special events). He is similar to his superboss incarnation from Dragon Quest V, and becomes enraged by anyone that inflicts a critical hit on him.

Estark is present as a rank X member of the Material family and the last member listed in that group. He is also the only rank X monster the player can obtain in the game outside of the Wildcard World Cup, though not until beating the game and the subsequent post-game challenge. Players can find him at rest within the sewers of Domus Isle once they obtain the key to get to him, a battle in order before he joins you. Amusingly, although awake when spoken to, Estark is sleeping at the start of the fight. He can be synthesized using a Psaro and Beetlebully.